Meeting Abstract

37.4  Tuesday, Jan. 5  Genetic recombination within Mytilus as evidence of past species distributions ROGNSTAD, R L*; HILBISH, T J; Univ. of South Carolina, Columbia; Univ. of South Carolina, Columbia rhiannon@biol.sc.edu

The Mytilus edulis (common blue mussel) complex is composed of three sister species (M. edulis, M. galloprovincialis, and M. trossulus) that are capable of interbreeding when they co-occur. Hybridization between these species has been extensively examined in many of the locations where they are sympatric. Studies of these and other hybrid zones provide information on the genetic mechanisms of speciation and evolution by describing patterns of recombination and selection. Interspecific variation in the gene encoding adhesive Mytilus foot protein-1 (mfp-1) has allowed the development of markers capable of distinguishing the three sister species. When used together, markers targeting the 5’ and 3’ ends of the mfp-1 coding sequence can be used to identify interspecies recombination within this large gene. Investigation of western European hybrid zones of M. edulis and M. galloprovincialis indicates interspecies recombination rates average about seven percent. Results also indicate significant variation in the number of recombinant alleles among size classes, with a greater frequency of recombinant alleles usually observed in smaller size classes. Comparison of recombinant allele frequency within the current hybrid zone with that of areas that were recently composed of hybrid populations reveals a significant reduction of recombinant alleles over time. Together these patterns suggest that natural selection occurs against recombinant alleles and that these genetic variants are being continuously regenerated within and spread from hybrid populations. Estimated selection coefficients based on these data predict hybrid zone movement similar to movement predicted based on changes in climatic variables.